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Flexible structures driven by smart actuators are promising alternatives for aquatic bionic propulsion vehicles. However, the hydrodynamic effects induced by viscous fluids on the dynamic response of flexible structures remain an ongoing challenge. Thus, this article presents a fluid-structure interaction dynamic model of a flexible underwater structure actuated by macro fiber composite actuators, and the underwater multimodal vibration characteristics are studied. The model is based on the extended Hamilton's principle, which considers the effects of hydrodynamic forces. The segmented mode shape functions of the flexible structure are derived using the assumed mode method. The study shows that the first two mode shapes of the beam predicted by the model agrees with the experimental results. The underwater dynamic responses of the flexible structure in a board band covering the first two resonance frequencies are also investigated at different actuation levels. The underwater results indicate that the first two resonance frequencies are 1.05 and 6.1 Hz respectively, basically consistent with the simulation ones (1.07 and 6.61 Hz). Correspondingly, the maximum transverse deflections at the end of the beam are 4.81 and 1.31 mm respectively, which are slightly lower than the predicted values of 5.75 and 1.62 mm. Therefore, the validity of the proposed coupled dynamic model is verified, which can be utilized to predict the multimodal dynamic responses of underwater flexible structures actuated by MFC or other smart actuators. [ABSTRACT FROM AUTHOR]

The traditional finite element model has the problems of high computational cost，more black-box operation，and lack of independent intellectual right. The analytical method is used to study the prediction of the vibration response of aircraft wall panels with macro fiber composite（MFC）patches under basic harmonic excitation. Based on classical laminate plate theory，electro mechanical coupling constitutive equations，and the energy method，the analytical model of the MFC-panel system under basic harmonic excitation is established. By employing velocity feedback control method and modal superposition principle，the vibration response of the structure system before and after active control under such an excitation load is successfully solved. The analytical model and its predictive results are extensively validated through the integration of literature data and experimental data obtained from a vibration testing system that is assembled. The results show that，compared to the literature results，the maximum deviation in the calculation of natural frequencies by the proposed model is less than 2%. Additionally，the maximum error in predicting the first two order resonance responses by the model is less than 8.6 %，and both of them are within an acceptable range.

Precision micro-manipulation tasks demand high-speed motion but low driving frequency for stick-slip actuators to achieve efficient operation and reduce friction wear. This paper presents a novel parasitic-type linear stick-slip actuator with macro fiber composites (MFCs). Unlike conventional piezoelectric actuators, the proposed stick-slip actuator has large single-step displacements and high motion consistency. It can realize high-speed motion under low driving frequency due to the superior properties of MFCs and the dual-drive method with a single driving foot. The actuator is devised based on a multi-beam-compliant driving mechanism, a pair of MFCs, and a slider. Also, an electromechanical dynamic model is proposed. A switching control strategy guarantees high positioning accuracy under large strokes. Finally, an experimental system is built. The single-step displacement can reach 367.7 μm with the dual-drive method. The actuator still has an effective stepping displacement of 63.4 μm even with a load of 2.1 kg. The maximal speed is 131.80 mm/s at a working frequency of 450 Hz. Thus, the actuator can realize mm/s motion with several Hertz driving voltages. Moreover, the maximum forward-reverse deviation only accounts for 1.31 % for a 2504 μm motion range, and the closed-loop motion resolution is 1.970 nm. Experiments verify the effectiveness and performance of the designed MFC stick-slip actuator. [Display omitted] • Macro-fiber-composite stick-slip actuator with large single-step displacements. • High forward-reverse motion consistency. • Electromechanical dynamic model for the MFC stick-slip actuator. • Nanoscale motion resolution using feedback control. [ABSTRACT FROM AUTHOR]

The subject of this article is an experimental analysis of the control system of a composite-based piezoelectric actuator and an aluminum-based piezoelectric actuator. Analysis was performed for both the unimorph and bimorph structures. To carry out laboratory research, two piezoelectric actuators with a cantilever sandwich beam structure were manufactured. In the first beam, the carrier layer was made of glass-reinforced epoxy composite (FR4), and in the second beam, it was made of 1050 aluminum. A linear mathematical model of both actuators was also developed. A modification of the method of selecting weights in the LQR control algorithm for a cantilever-type piezoelectric actuator was proposed. The weights in the R matrix for the actuator containing a carrier layer made of stiffer material should be smaller than those for the actuator containing a carrier layer made of less stiff material. Additionally, regardless of the carrier layer material, in the case of a bimorph, the weight in the R matrix that corresponds to the control voltage of the compressing MFC patch should be smaller than the weight corresponding to the control voltage of the stretching MFC patch. [ABSTRACT FROM AUTHOR]

This study focuses on addressing the issue of unwanted vibrations commonly encountered in various fields by designing an Active Vibration Cancellation (AVC) structure using a flexible piezoelectric composite material macro fiber composite (MFC). A comparative performance analysis was conducted between the AVC and a traditional passive gel that continuously absorbs vibrations. The results showed that AVC was more effective in mitigating vibrations, making it a promising solution for vibration control. The results of this study from extensive vibration–sensing experiments and comparisons revealed that AVC effectively cancels the vibrations and vibration absorption performance of the passive gel. These findings underline the potential of AVC as an efficient method for eliminating and managing undesired vibrations in practical applications. Specifically, AVC demonstrated a high vibration cancellation ratio of approximately 0.96 at frequencies above 10 Hz. In contrast, passive gel exhibited a relatively consistent vibration absorption ratio, approximately 0.70 to 0.75 at all tested frequencies. These quantitative findings emphasize the superior performance of AVC in reducing vibrations to levels below a certain threshold, demonstrating its efficacy for vibration control in real-world scenarios. [ABSTRACT FROM AUTHOR]

This article presents a comparison of hysteresis courses in the motion of a two-input actuator (bimorph) and hysteresis in the motion of a single-input actuator (unimorph). The comparison was based on the results of laboratory and numerical experiments, the subject of which was an actuator built of three layers: a carrier layer from a glass-reinforced epoxy laminate and two piezoelectric layers from Macro Fiber Composite. The layers were glued together, and electrodes in the Macro Fiber Composite layers were connected to a system that included an analogue/digital board and a voltage amplifier. The main purpose of this research was to compare the characteristic points of the hysteresis curves of the displacement of the bimorph actuator with the characteristic points of the hysteresis curves of the unimorph actuator. Based on the research results, it was noticed that, in the bimorph, the maximum hysteresis and mean hysteresis values increase faster than the maximum displacement of a beam tip. However, values of characteristic input voltages for hysteresis loops—voltage corresponding to a maximum displacement of the actuator beam tip and voltage corresponding to maximum hysteresis—are almost the same for the bimorph and unimorph. From a practical point of view, it was noticed that the unimorph is a better choice compared to the bimorph in applications in which high changes in frequencies of input voltages appear. [ABSTRACT FROM AUTHOR]

This work proposes a novel methodology for planning the motion of fish-like soft robots actuated by macro-fiber composite (MFC) pairs. These structures should mimic oscillatory and undulation movements, which can be accomplished if the amplitude of the tail motion is larger than that of the head motion. Design strategies, such as the use of concentrated and distributed masses, are addressed to mimic fish-like motion since they guarantee suitable mode shapes for the structure. The motion planning proposal explores a model-based predictive control (MPC) strategy for deriving the input signals for the MFC actuators. This model-based control strategy requires the use of reasonably small-sized models. This is accomplished by extracting modal state-space models based on the free–free Euler–Bernoulli beam theory considering the electro-mechanical coupling of the MFC actuator pairs. Numerical results demonstrate the capability of the proposal for deriving bounded input signals that generate oscillatory and undulation movements even in the presence of disturbances. This general approach can be further extended for other applications. [ABSTRACT FROM AUTHOR]

This paper analyzes a piezoelectric system made of a smart lead zirconate material. The system is composed of a monolithic PZT (piezoelectric ceramic) plate made of a ceramic-based piezoelectric material. The experiment was conducted on a test stand with a GUNT HM170 wind tunnel and a special measurement system. The developed bluff-body shape mounted on an elastic beam with a piezoelectric was mounted on a mast with arms. Springs were fixed on the arms to limit the movement of the test object. Air flow velocity in the wind tunnel and forced vibration frequencies were changed during the tests. The recorded parameters were an output voltage signal from the piezoelectric element and linear accelerations at selected points of the test object. The highest energy efficiency of the tested system was specified from mechanical vibrations and air flow. The results of the tests are a resonance curve for the tested system and a correlation of RMS voltage and acceleration as a function of the velocity of air flow for the excitation frequency f ranging from 1 to 6 Hz. The tests specified the area where the highest output voltage under the given excitation conditions is generated. [ABSTRACT FROM AUTHOR]

This article presents a comparison of the course of a creep phenomenon in the control system of a bimorph actuator, in which control voltages were applied to both piezoelectric layers, with the course of the creep phenomenon in the control system of a unimorph actuator, in which a control voltage was applied to only one piezoelectric layer. The bimorph actuator was built from two layers of piezoelectric composite, macro fiber composite was applied, and a carrier layer made of epoxy laminate was used for production of printed circuit boards. A comparative analysis was carried out on the basis of 22 laboratory experiments in which the vision system was used to measure a displacement change of six points of the bimorph actuator structure. Based on the results of laboratory experiments, it was noted that the duration of a transient part is approximately the same in a system with a control voltage applied to one MFC patch as in a system with control voltages applied to two MFC patches. In the system with control voltages applied to two MFC patches, the position change due to the creep process is more than two times bigger in comparison to the system with the control voltage applied to one MFC patch. [ABSTRACT FROM AUTHOR]

Energy collection in a capacitor, which was charged by four connection structures of Macro Fiber Composite (MFC) patches, was the subject of laboratory research. The first structure was the delta circuit created by three MFC patches and connected with a three-phase rectifier; the second structure was the delta circuit created by three MFC patches and connected with a three-phase rectifier; the third structure was the parallel connection of three circuits, each of which consisted of an MFC patch and a full bridge rectifier; and the fourth structure the series connection of three circuits, each of which consisted of an MFC patch and a full bridge rectifier. Laboratory experiments were carried out on a laboratory stand which consisted of a rotating shaft, three MFC patches powering an energy storage system, and a data acquisition system. The star connection generated the highest values of voltage across a capacitor in the long time period. The delta connection produced the highest capacitor-charging power. The shortest time to reach a target voltage on the capacitor equal to a few volts was achieved by use of the delta or parallel connection. The delta connection generated target voltage equal to a few volts across a capacitor in the shortest time at a lower level of stress in the shaft, but the difference between the charging times by the delta circuit and by the parallel connection decreased as the stress in the shaft increased. [ABSTRACT FROM AUTHOR]

• A novel active-passive integrated actuator for micro-vibration isolation is devised. • A dominant-frequency-correction hysteresis modeling strategy is proposed. • A FEFC requiring merely displacement response feedback is developed. • The FEFC can achieve weak-side-effect resonance suppression. • The proposed APIA-MFC has great potential for engineering applications. Micro-vibration suppression is crucial for satellites to ensure high imaging performance of optical loads. Herein, an active-passive integrated actuator based on macro fiber composite for micro-vibration isolation is proposed and investigated. Integrated passive and active vibration suppression is achieved by arraying a composite laminated beam consisting of the stiffness layer, damping layer and macro fiber composite layer. A dominant-frequency-correction hysteresis modeling strategy is devised to describe the asymmetric and rate-dependent voltage-force hysteresis of the proposed actuator. By treating the correction as a disturbance, the voltage-force hysteresis is compensated in combination with an extended state observer. In order to achieve resonance suppression, a full-estimation-feedback controller featuring merely displacement response feedback is developed exploiting the estimation of the extended state observer as feedback. Simulation results verify that the full-estimation-feedback controller is capable of suppressing the resonance peak with weak adverse effects on the transmissibility in the isolation band. Finally, experiments are performed to identify the voltage-force hysteresis model and evaluate the vibration isolation performance. Periodic and sweep excitation test results demonstrate that in passive mode, the actuator has a small resonance frequency of 2.3 Hz and a wide isolation band starting from 3.5 Hz. With the full-estimation-feedback controller, the resonance peak is effectively suppressed using a single signal feedback, while maintaining excellent vibration attenuation within the isolation band. The proposed actuator provides a paradigm for the design of active-passive integration vibration isolators for broadband micro-vibration suppression, which holds significant promise in enhancing the effectiveness of current observation missions. [ABSTRACT FROM AUTHOR]

In this paper the problem of vibration reduction is considered. Generally, mechanical vibrations occurring during the operation of a system are undesirable and may have a negative effect on its reliability. A finite element model of a single active blade is developed using the Abaqus software. This structure consists of a multi-layer glass-epoxy composite beam with an embedded macro fiber composite (MFC) piezoelectric actuator. For vibration control the use of a positive position feedback (PPF) controller is proposed. To include the PPF controller in the Abaqus software, a special subroutine is created. The developed control algorithm code makes it possible to solve an additional differential equation by the fourth order Runge- Kutta method. A numerical dynamic analysis is performed by the implicit procedure. The beam responses with and without controller activation are compared. The control subsystem model also includes the hysteresis phenomenon of the piezoelectric actuator. Numerical findings regarding the PPF controller’s effectiveness are verified experimentally. [ABSTRACT FROM AUTHOR]

Dynamic oscillating behavior of the flexible structure immerged in viscous fluids has attracted growing attention and been widely used in various practical applications. A general electricity-structure-fluid coupled model for the forced dynamic responses of a cantilever immersed in fluids, with partially distributed macro fiber composite, is proposed in this paper. Based on the classical Euler–Bernoulli beam theory, the first mass-normalized mode shape of the cantilever with partially bonded macro fiber composite is determined using assumed mode method. The attachment of the macro fiber composite actuators stiffens the macro fiber composite-bonded portion of the cantilever. The established mode shape matches perfectly with experimental results. Considering the macro fiber composite actuator as a set of representative elements connected in parallel, the internally actuation moment provided by the macro fiber composite actuators is obtained. The hydrodynamic load caused by the surrounding fluids, decomposed into the added mass and hydrodynamic damping parts, is also added to the theoretical model in the frequency-domain form. The predicted in-air and underwater dynamic behaviors of the flexible beam are consistent with the experimental results at different auction levels. Thus, the obtained general electricity-structure-fluid coupled model can be used to predict the forced dynamic responses of flexible structure with partially bonded actuators immersed in fluids. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Continuous trailing-edge flap has many advantages over conventional discrete flap in helicopter rotor vibration reduction applications, such as light weight, compact structure and stable airflow. Macro fiber composite is chosen as the actuating material. A blade section with a continuous trailing-edge flap is designed based on NACA23012 airfoil, and its materials are selected and analyzed. The influence of continuous trailing-edge flap on airfoil aerodynamic characteristics is analyzed by fluid-solid coupling method. Results show that continuous trailing-edge flap can output sufficient deflection under the working conditions of helicopter blade, including angle of attack as well as Mach number, and improve aerodynamic lift and moment of the blade profile significantly, which demonstrates the potential value of continuous trailing-edge flap in rotor vibration reduction applications.

In this study, vibration control was achieved using macro fiber composite actuators initiated by feedback from polyvinylidene difluoride (PVDF) membrane sensors. First, the structure mode was found using the finite element method after which simulation of the effect of piezoelectric actuators on the structure as well as a feasibility investigation was carried out. The ANSYS Workbench was used for parametric design and to determine the best position for the actuators. Structure vibration in different modes was measured using PVDF membrane sensors for feedback control and to investigate the vibration reduction effect achieved with three individual controllers. The pros and cons of active vibration reduction control were also examined in several different modes. The experimental results obtained with several types of vibration reduction control were compared: Type-1 fuzzy control, Type-1 adaptive fuzzy control, and the vibration reduction effect of an adaptive neuro-fuzzy inference system. The results showed that the adaptive neuro-fuzzy inference system controller was the best choice under the experimental conditions used in this study. [ABSTRACT FROM AUTHOR]

Over the last decade, vibration energy harvesting has received substantial attention of many researchers. Piezoelectric materials are able to capture energy from ambient vibration and convert it into electricity which can be stored in batteries or utilized to power small electronic devices. In order to benefit from the 33-mode of the piezoelectric effect, interdigitated electrodes have been utilized in the design of macro fiber composites which are made of piezoelectric fibers of square cross sections embedded into an epoxy matrix material. This paper presents an analytical model of a macro fiber composite bimorph energy harvester using the 33-mode. The mixing rule is applied to determine the equivalent and homogenized properties of the macro fiber composite structures. The electromechanical properties of a representative volume element composed of piezoelectric fibers and an epoxy matrix between two successive interdigitated electrodes are coupled with the overall electro-elastodynamics of the harvester utilizing the Euler–Bernoulli theory. Macro fiber composite bimorph cantilevers with diverse widths are simulated for power generation when a resistive shunt loading is applied. Stress components in the Kapton layers, which are typically a part of any macro fiber composite patch, and in the bonding layers have been included in the model contrary to previously published studies. Variable tip mass, attached at the free end of the beam, is utilized in this paper to tune the resonance frequency of the harvester. The generated power at the fundamental short circuit and open circuit resonance frequencies of harvesters having three different widths is analyzed. It has been observed that higher electrical outputs are produced by the wider macro fiber composite bimorph using (M8528-P1 patches). [ABSTRACT FROM AUTHOR]

Copyright of Technisches Messen is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The main drawback in many electronic devices is the duration of their batteries. Energy harvesting provides a solution for these low-consumption devices. Piezoelectric energy harvesting use is growing because it collects small amounts of clean energy and transforms it to electricity. Synthetic piezoelectric materials are a feasible alternative to generate energy for low consumption systems. In addition to the energy generation, each pressure cycle in the piezoelectric material can provide information for the device, for example, counting the passage of people. The main contribution of this work is to study, build, and test a low-cost energy harvesting floor using piezoelectric transducers to estimate the amount of energy that could be produced for a connected device. Several piezoelectric transducers have been employed and analyzed, providing accurate results. [ABSTRACT FROM AUTHOR]

This article investigates the modeling of macro fiber composite-actuated laminate plates with distributed actuator patches. The investigation details an analytical and finite element modeling, with experimental validation of the bending strain and deflection of an epoxy E-glass fiber composite laminate. An analytical approach is also developed to estimate the plate deflection from the experimental strain measurements. The analytical method uses direct integration of single dimensional plate bending moments obtained by strain-induced shear moments from the macro fiber composite actuators. Finite element analysis software was used with the composite laminate modeled in ANSYS ACP. The results from both analytical and numerical models show good agreement with the experimental results, with strain values agreeing within 20 ppm and the maximum difference in deflection not exceeding 0.1 mm between models. Finally, an application of the analytical model for developing morphing aerofoil designs is demonstrated. [ABSTRACT FROM AUTHOR]

Studies on the hydrodynamics of underwater flexible structures are gaining significant attention. To improve the performance and stability of underwater flexible structures in complex water environments, new control strategies must be proposed. This study proposes underwater rate-dependent hysteresis compensation and iterative learning control (ILC) of the flexible structure actuated by macro fiber composites (MFC). The underwater rate-dependent hysteresis model of the MFC partially-actuated structure consists of two components: a modal state space model characterizing the underwater rate-dependent behavior, and a modified Prandtl–Ishlinskii (MPI) model describing the bias bipolar hysteresis. The MPI model is combined with a PI and a polynomial model of fractional orders. To obtain a unique analytic inverse model, constraints for the inverse are proposed. Results show the varying bias ellipse-like hysteresis behaviors are well captured. Tracking performances are greatly improved with the feedforward compensator. Furthermore, an ILC is developed to address model uncertainties and unsteady hydrodynamics. The convergence and robustness of the ILC are discussed. Parameters of the zero-phase and learning filters are determined. Experimental results demonstrate the tracking errors of the underwater structure are significantly reduced. These findings are meaningful for the realization of flexible structures for marine engineering, underwater robots and other fields. • Underwater rate-dependent hysteresis compensation and iterative learning control are proposed. • A modified Prandtl-Ishlinskii hysteresis model combines a PI model with polynomials of fractional orders. • Constraints for the unique analytic inverse of polynomials of fractional orders are defined. • A modal state space model is developed to characterize the underwater rate-dependent behavior. • A zero-phase low-pass filter is proposed to address the phase lag caused by the Q -filter. [ABSTRACT FROM AUTHOR]

A cantilever beam, manufactured from a steel-carrying substrate and two patches of Macro Fiber Composite of P2 type, was a subject of laboratory research. MFC patches were glued on both sides of the carrying substrate and were parallelly connected. An experimental determination of an optimal resistance for both energy harvesting and vibration passive damping of the cantilever beam was the purpose of the conducted laboratory research. The research contained 10 experiments in which courses of the energy-harvesting process and resistive passive damping of vibration were estimated. Energy harvesting was estimated by measurements of the generated current for the given load-resistance values. Resistive passive damping of vibration was assessed by using a vision method that enabled the displacements’ measurements of 10 selected points in the beam structure for the given shunt-resistance values. Values of both load resistance and shunt resistance were chosen on the basis of analytically calculated optimal load resistance and optimal shunt resistance. On the basis of the conducted experiments, the resistance range for which both the energy-harvesting process and the vibration-damping process are most effective was determined.

Four arrays of three MFC patches, glued onto a rotating shaft, were compared in laboratory research. The first array was based on a delta circuit and equipped with one three-phase rectifier; the second array was based on a star circuit and equipped with one three-phase rectifier; the third array was based on parallel connection and equipped with three full-bridge rectifiers; and the fourth array was based on a series connection and equipped with three full-bridge rectifiers. The array based on a delta circuit generated the highest value of maximal electric power in comparison to the rest of arrays. It was experimentally observed that the arrays based on delta or star circuits of MFC patches and equipped with one three-phase rectifier generated a higher value of maximal power than arrays based on the connections of three full-bridge rectifiers, connected in parallel or in series. The array based on parallel connection generated the highest maximal value of current in comparison to rest of arrays for low values of load resistance (from 10 kΩ to 40 kΩ depending on the experiment). For higher values of load resistance arrays based on delta circuits and star circuits generated higher values of current than the array based on parallel connection.

In this paper, the nonlinear dynamic responses of a piezoelectric cantilever plate near the first-order and second-order natural frequencies under the action of electromechanical coupling are studied by experiments and finite element (FE) methods. The influence of different excitation frequencies on the dynamical characteristics of piezoelectric cantilever plates is analyzed with the fixed excitation amplitude. First, an experimental setup is built, including a carbon fiber cantilever plate attached to a macro fiber composite (MFC) sheet. Then, the electromechanical coupling excitations are subjected to the plate with different frequencies, which are chosen near the first and second-order natural frequencies of the plate. The piezoelectric cantilever plate has periodical motions under a lower frequency excitation, and the motions of the plate become more complex after another high frequency excitation added in the physical field. The experimental results show that the motion of the piezoelectric cantilever plate changes from stable to unstable with high–low coupled resonant frequencies. At last, the FE study is carried out to compare and verify the experimental results and the effects of isotropic and orthotropic materials on the accuracy of natural frequencies results are also compared. [ABSTRACT FROM AUTHOR]

A new piezoelectric composite, macro fiber composite (MFC) is recombined with piezoceramic fibers, an epoxy resin basal body, and an interdigitated electrode. It has been widely applied in vibration reduction and deformation control of thin-walled structures, due to its great deformability and flexibility. Research on its actuation performance is mostly concentrated on the MFC actuating force calculation based on classical plate theory (CPT), and the overall modeling of MFC and its structure. However, they have some deficiencies in the tedious calculating process and neglect of shear deformation, respectively. To obtain a precise MFC actuating force, the sinusoidal shear deformation theory (SSDT) is adopted to deduce the MFC actuating force formula, and global–local displacement distribution functions are introduced to help the MFC laminated plate structure satisfy the deformation compatibility and stress balance. For instance, in the end displacement calculation of the MFC laminated beam structure. The experimental result of the MFC laminated beam is compared with those of the MFC actuating force based on SSDT and on CPT, which indicates that the MFC actuating force formula based on SSDT can reach higher computational accuracy. [ABSTRACT FROM AUTHOR]

Highlights • A robust numerical approach has been proposed to solve for follower forces in compliant mechanisms. • Linear and nonlinear finite element methods have been adopted to solve for large deflection with complicated geometries and forces. • Experiments have been performed for beams with follower forces and are validated with the simulated results based on the proposed model. • The efficacy of the presented algorithms in the design of compliant structures is shown through a wing morphing example. Graphical abstract Abstract A linear finite element and a nonlinear finite element solution scheme have been proposed to obtain the deflection of a compliant structure, modeled as a cantilever beam, under the action of a follower force acting at the end, in addition to any additional arbitrary loading. The developed techniques have been compared with a numerical technique available in literature, wherein, nonlinear Euler–Bernoulli beam theory is used in an iterative scheme. It was found that the results of the nonlinear finite element algorithm exactly match the solution from the available scheme; while on the other hand, the linear finite element gives fairly close results at a higher rate of convergence. Experiments are carried out to validate the two proposed solution techniques. Two example problems have been solved, which show the practical application of this numerical scheme, in the design of mechanisms actuated by smart materials like shape memory alloys (SMA) and macro fiber composites (MFC), in the process, obviating the limitations of the available techniques in solving such problems. [ABSTRACT FROM AUTHOR]

Highlights • A condition monitoring system based on non-destructive tests by ultrasonic waves was used to analyse wind turbine blades. • This paper employs an approach that considers advanced signal processing and machine learning to determine the thickness of the dirt and mud in a WTB. • Wavelet transform and Feature selection are employed to remove non-useful data. • Pattern recognition is carried out by Supervised Learning Classifiers based on statistical models to classify the signals. The results provided by PCA show an improvement over the AR results. • The novelty of this work is focused on applying this approach to detect and diagnose mud and dirt in WTB. Abstract Dirt and mud on wind turbine blades (WTB) reduce productivity and can generate stops and downtimes. A condition monitoring system based on non-destructive tests by ultrasonic waves was used to analyse it. This paper employs an approach that considers advanced signal processing and machine learning to determine the thickness of the dirt and mud in a WTB. Firstly, the signal is filtered by Wavelet transform. FE and Feature Selection(FS) are employed to remove non-useful data and redundant features. FS selects the number of the most significant terms of the model for fault detection and identification, reducing the dimension of the dataset. Pattern recognition is carried out by the following supervised learning classifiers based on statistical models to calculate and classify the signal depending on the fault: Ensemble Subspace Discriminant; k-Nearest Neighbours; Linear Support Vector Machine; Linear Discriminant Analysis; Decision Trees. Receiver Operating Characteristic analysis is used to evaluate the classifiers. Neighbourhood Component Analysis has been employed in feature selection. Several case studies of mud on the WTB surface have been considered to test and validate the approach. Autoregressive (AR) model and Principal Component Analysis (PCA) have been employed to FE. The results provided by PCA show an improvement on the AR results. The novelty of this work is focused on applying this approach to detect and diagnose mud and dirt in WTB. [ABSTRACT FROM AUTHOR]

A beam containing a piezoelectric layer or layers is used for piezoelectric harvesting from various processes. The structure of the beam is made by gluing the piezoelectric material on one side (unimorph) or both sides (bimorph) of a carrying substrate. Two piezoelectric layers, glued on both sides of the substrate, may be electrically parallel or series connected. This paper presents an experimental analysis of the impact of parallel and series connections of two Macro Fiber Composite (MFC) MFC patches in a bimorph on the charging of a capacitor. In experiments, the effective charging process of the capacitor was obtained both for parallel and series connection of two MFC patches. The bimorph with a parallel connection generated a larger capacitor charging power than the bimorph with a series connection in the range of voltage across the capacitor from 1 to 18 V. However, the bimorph with a series connection was more effective than a parallel connection for voltage across the charged capacitor from 18 to 20 V. The maximum capacitor charging power generated by the bimorph, in which two MFC patches were parallel connected, was 1.8 times larger than that generated by the bimorph with a series connection and was 3.3 times larger than that generated by a unimorph with one MFC patch. The impact of level of voltage across the capacitor on its discharging process has a significant meaning for the ratio of maximum power between bimorphs and between the bimorph and unimorph.

The main drawback in many electronic devices is the duration of their batteries. Energy harvesting provides a solution for these low-consumption devices. Piezoelectric energy harvesting use is growing because it collects small amounts of clean energy and transforms it to electricity. Synthetic piezoelectric materials are a feasible alternative to generate energy for low consumption systems. In addition to the energy generation, each pressure cycle in the piezoelectric material can provide information for the device, for example, counting the passage of people. The main contribution of this work is to study, build, and test a low-cost energy harvesting floor using piezoelectric transducers to estimate the amount of energy that could be produced for a connected device. Several piezoelectric transducers have been employed and analyzed, providing accurate results.

Abstract This work investigates the aeroelastic stability boundary of curved composite panels with embedded Macro Fiber Composite (MFC) actuators in the supersonic airflow. Prescribed voltages are statically applied to the MFC actuators, inducing a pre-stress field which results in an additional stiffness effect on the curved panels, thus changing the aeroelastic stability boundary of curved composite panels. The principle of virtual work is applied to develop the equations of motion for the nonlinear flutter of curved composite panels with embedded MFC actuators. The Von Karman large deflection panel theory and the first order quasi-steady piston theory are adopted in the formulation. The Newton-Raphson method is employed to determine the static aeroelastic deflection under the applied voltages, and an eigenvalue solution is adopted to predict the aeroelastic stability boundary of the curved panels. Numerical results show that the influence of the applied voltages is distinct for the curved composite panels with different curvatures. In addition, the lamination angles of the MFC actuator and the temperature elevations will also significantly affect the aeroelastic stability boundary of curved composite panels in the supersonic airflow. [ABSTRACT FROM AUTHOR]

Highlights • A novel piezoelectric harvester with sandwich substrate is proposed and analyzed. • Theoretical model for designing and optimizing sandwich harvester is derived. • Proposed sandwich harvester has low resonant frequency and high voltage output. • Accuracy and superiority of the theory are verified by simulation and experiment. • Influence of material/geometric parameters on harvester's performance is studied. Abstract Piezoelectric energy harvesting from ambient vibration sources has great potential for powering microelectronic devices and wireless sensors. Almost all the conventional piezoelectric energy harvesters (CPEHs) in the literature have been designed with a single metallic layer as substrate along with the piezoelectric material bonded over it. In this work, a novel sandwich structure is used as substrate for designing harvester. The substrate structure comprises of a soft-core material sandwiched between metallic layers. The proposed sandwich piezoelectric energy harvester (SPEH) has lower resonant frequency and generates higher voltage output than the CPEH with the same geometrical dimension. Furthermore, the SPEH offers high design flexibility in terms of tuning the resonant frequency through selection of materials and geometric parameters for the core and metal layers. The mathematical formulation of a generalized electromechanical model of the SPEH is developed using the Lagrange approach. The natural frequencies, displacement and voltage frequency response functions of the harvester are obtained analytically. A single-degree-of-freedom model for the SPEH is also derived. Subsequently, the analytical modeling is validated by finite element simulations and experimental results. When excited at 0.1 g, the SPEH generates 18.8% more voltage output at resonance as compared with a CPEH with the same geometrical dimension and tip mass accompanied by 24% reduction in resonant frequency. At 30 Hz resonance frequency, CPEH generates open-circuit voltage 17.6 V using 15 g of tip mass whereas SPEH uses only 8.2 g of tip mass to generate 16.6 V. SPEH generates 130.8 μW, 426.6 μW and 1158.0 μW at base accelerations 0.05 g, 0.1 g and 0.2 g with optimal resistance, respectively. Finally, the influence of geometric and material properties of core and metallic layers on the performance of SPEH are analyzed comprehensively. The proposed novel SPEH together with its analytical modeling is intended to serve as a basis for future sandwich harvester designs. [ABSTRACT FROM AUTHOR]

The elastic instabilities associated with buckling in bistable structures have been harnessed toward energy-based and motion-based applications, with significant research toward energy harvesting and morphing. Often combined with smart materials, structural prototypes are designed with a single application in mind. Recently, a novel method of inducing bistability was proposed by bonding two piezoelectrically actuated macro fiber composites in a [0MFC/90MFC]T layup and releasing the voltage post cure to yield two cylindrically stable configurations. Since the macro fiber composites are simultaneously the actuator and host structure, the resulting efficiencies enable this bistable laminate to be multifunctional, with both broadband energy harvesting and snap-through morphing capabilities. This article experimentally characterizes the vibration-based energy harvesting performance of the laminate to enable morphing. Through frequency sweeps across the first two modes of both states, the laminate exhibits broadband cross-well dynamics that are exploited for improved power generation over linear resonant harvesters. Besides single-well oscillations, snap-throughs are observed in intermittencies and subharmonic, chaotic, and limit cycle oscillations. The maximum power output of each regime and their charge durations of an energy harvesting module are assessed. The laminate’s capabilities are then bridged by utilizing harvested energy in the charged module to initiate snap-through actuation. [ABSTRACT FROM AUTHOR]

Aerothermoelastic flutter properties of nonlinear composite laminated panels in supersonic airflow are studied, and investigations on active flutter and aerothermal postbuckling suppression for the panels with time-dependent boundary conditions are also carried out using macro fiber composite actuator and sensor. The von Karman strain–displacement relation in conjunction with the supersonic piston theory is applied in structural modeling. Nonlinear dynamic equations of motion for the structural system are established using Hamilton’s principle and the assumed mode method. Frequency- and time-domain methods are used to investigate the aerothermoelastic characteristics and active flutter and aerothermal postbuckling suppression of the panels. Effects of aspect ratio and ply angle on the nonlinear aerothermoelastic behaviors are studied. The displacement feedback control is used to conduct the active flutter and postbuckling suppression. The nonlinear output controller consisting of a linear quadratic regulator and a nonlinear state estimator of extended Kalman filter is also used in designing the controller. Controlled vibration responses of the structural system under the two different controllers are compared. The results show that the developed linear quadratic regulator/extended Kalman filter controller is more effective than the displacement feedback control controller in flutter and postbuckling control of the panels with time-dependent boundary conditions in supersonic airflow. [ABSTRACT FROM AUTHOR]

Over the past decades, thanks to the progresses being made in low-power microelectronics, wireless technology, and energy harvesting techniques, we are observing an impressive increase in the use of wearable devices. Kinetic human energy harvesting is the most efficient and practical method to power them reducing the need of batteries replacement since walking or running is how humans already expend much of their daily energy. The present energy harvesting technologies still have several limitations. In this work, thanks to a mechanical framework specifically designed to reproduce the kinematic of a knee joint and actuated using recorded human motion patterns, we demonstrate the feasibility of the nonresonant employment of the macrofiber composites (MFCs) to scavenge energy from the various human body movements. Both the energy of periodic and aperiodic motions can be harvested. The electrical characteristics of the whole system focusing on the maximum power point of the MFC have been investigated to optimize the system power output. [ABSTRACT FROM PUBLISHER]

A new piezoelectric composite, macro fiber composite (MFC) is recombined with piezoceramic fibers, an epoxy resin basal body, and an interdigitated electrode. It has been widely applied in vibration reduction and deformation control of thin-walled structures, due to its great deformability and flexibility. Research on its actuation performance is mostly concentrated on the MFC actuating force calculation based on classical plate theory (CPT), and the overall modeling of MFC and its structure. However, they have some deficiencies in the tedious calculating process and neglect of shear deformation, respectively. To obtain a precise MFC actuating force, the sinusoidal shear deformation theory (SSDT) is adopted to deduce the MFC actuating force formula, and global−local displacement distribution functions are introduced to help the MFC laminated plate structure satisfy the deformation compatibility and stress balance. For instance, in the end displacement calculation of the MFC laminated beam structure. The experimental result of the MFC laminated beam is compared with those of the MFC actuating force based on SSDT and on CPT, which indicates that the MFC actuating force formula based on SSDT can reach higher computational accuracy.

Delamination in Wind Turbine Blades (WTB) is a common structural problem that can generate large costs. Delamination is the separation of layers of a composite material, which produces points of stress concentration. These points suffer greater traction and compression forces in working conditions, and they can trigger cracks, and partial or total breakage of the blade. Early detection of delamination is crucial for the prevention of breakages and downtime. The main novelty presented in this paper has been to apply an approach for detecting and diagnosing the delamination WTB. The approach is based on signal processing of guided waves, and multiclass pattern recognition using machine learning. Delamination was induced in the WTB to check the accuracy of the approach. The signal is denoised by wavelet transform. The autoregressive Yule–Walker model is employed for feature extraction, and Akaike’s information criterion method for feature selection. The classifiers are quadratic discriminant analysis, k-nearest neighbors, decision trees, and neural network multilayer perceptron. The confusion matrix is employed to evaluate the classification, especially the receiver operating characteristic analysis by: recall, specificity, precision, and F-score. [ABSTRACT FROM AUTHOR]

• Morphing wing technology enhances adaptability and versatility in drones' flight. • Macro Fiber Composite actuators enable in-flight camber variation. • Experimental tests permit the characterization of the wing's deformation. • Finite Element Analysis allows for analyzing different actuator configurations. • Actuators located spanwise enhance lateral stability by elevating wingtip. The purpose of this paper is to show the advantages of using a smart composite in a micro air vehicle (MAV) equipped with morphing wing technology. A Macro Fiber Composite (MFC) actuator is attached to the wing's bottom surface to modify the wing camber during the mission. This material allows the MAV to be optimized according to each flight, thus making it more versatile and attractive to the market. The elongation of the lower surface when a positive voltage is applied to the actuator is translated to an increment in camber, which results in an increment in the maximum lift coefficient, thus enabling the vehicle to fly slower to adapt to any payload. Besides, a reduction in camber results in an increase in aerodynamic efficiency, which improves range and endurance. Several tests of the MAV at prototype level have been carried out at INTA, so as to demonstrate the feasibility of implementing MFC actuators to control and manoeuvre these vehicles. The use of this material in aerospace industry opens up various fields of research in aerospace engineering, such as new features in flight mechanics and aerodynamic performance and new strategies in the design of flight stability and control laws. [ABSTRACT FROM AUTHOR]

Macro fiber composite (MFC) has been extensively used in actuator/sensor/harvester applications. Fatigue due to cyclic high electric fields in actuator applications has been studied extensively. However, fatigue failure of MFC due to high stress or strains in energy harvesting applications has attracted little attention. The aim of the study is to obtain the upper limit of dynamic strain on MFC which can be used as failure limit in the design process of piezoelectric energy harvesters (PEHs). The examined PEH is comprised of a cantilever beam made of aluminum and a patch of MFC bonded at its root for power generation. Energy harvesting tests are conducted at various base accelerations around 30 Hz (near resonant frequency) and the voltage output and maximum strain on MFC are measured. Severe loss in the performance of the harvester is observed within half million cycles of testing at high strain amplitude. Hence several reliability tests for extended periods of time are carried out at various strain amplitudes. The harvesters are tested at resonant frequencies around 30 Hz and 135 Hz for over 20 million and 60 million cycles, respectively. Degradation in voltage output, change in natural frequency and formation of cracks are considered as failures. Based on the experimental results, an upper limit of 600 μϵ is proposed as the safe amplitude of strain for reliable performance of MFC. Tensile tests are also carried out on MFC patches to understand the formation of cracks and shift in resonant frequency at low strains. It is observed that cracks are formed in MFC at strains as low as 1000 μϵ. The observations from this work are also applicable to MFC bending actuators undergoing cyclic strains. [ABSTRACT FROM AUTHOR]

The Pin-Force Model (PFM) and the Enhanced Pin-Force Model (EPFM) for analyzing the mechanical behavior of a composite beam with active materials are widely used because of simplicity and adaptability. However, the PFM and the EPFM overestimated the deformation of composite beams under a small thickness ratio of substrate and actuator. In this paper, the reasons for the above phenomenon are analyzed first. Then a revised model named Modified Pin Force Model (MPFM) is proposed, which involves the factors neglected in previous models. The detailed derivation and description of the models for both unimorph and bimorph bonding forms are given. The bending curvature of a composite beam predicted by the MPFM is compared with that obtained by both the Euler-Bernoulli beam model and finite element analysis. The result shows a good consistency even in the small thickness ratio. Experiments based on MFC materials were performed to validate the MPFM. The results demonstrate that the proposed model can well predict the bending deformation of a composite beam with mounted actuators in the small thickness ratio, which extends the application range of pin-force models. [ABSTRACT FROM AUTHOR]

This paper describes the fabrication and performance results of a magnetoelectric macro fiber composite (ME MFC). The magnetoelectric composite was fabricated by bonding a magnetostrictive layer to a piezoelectric layer using a novel approach of low temperature transient liquid phase (LTTLP) bonding. The composite was diced into 150 micron wide fibers and bonded to a custom designed copper flexible circuit using a spin coated low viscosity room temperature curing epoxy. ME MFC’s with varying ferrite thicknesses of 0.6 mm and 0.5 mm were fabricated and characterized for energy harvesting. The composite with 0.6 mm ferrite thickness achieved an open circuit voltage of 101 mV (ME voltage coefficient of 6740 mV/cmOe) and peak power of 3.1 nW across 356 kΩ matching load at 264 Hz. [ABSTRACT FROM AUTHOR]

In this paper, we present a vibration energy harvester using a spherical permanent magnet as springless proof mass and a magnetoelectric laminate structure composed of MSMA (magnetic shape memory alloy) and MFC (macro fiber composite) in d 31 or d 33 operational modes. Combination of transduction mechanisms, including magnetoelectric effect and impact-induced vibration of the magnetoelectric laminate composite, generates power from low frequency excitation such as human-body-induced motion. Two different types of magnetoelectric laminate composite based power generators have been fabricated, tested and compared. Moreover, the contributions of individual transduction mechanisms have been analyzed experimentally. Maximum peak-to-peak open circuit voltage of 16.4 V has been obtained in response to a 3 g vibration at 15 Hz for device with d 33 mode MFC. Device with d 31 mode MFC generated maximum output power of 11.2 μW in vibration exciter test and 82.5 μW in manual vibration test across an 800 Ω load. Based on the experimental observations, an impact-based harvester with d 31 mode MFC has been proposed, which generated improved output power of 245.6 μW. [ABSTRACT FROM AUTHOR]

This research examines the application of Macro-Fiber Composites on substrate materials in the form of unimorph actuators. The intent is to characterize the behavior of the unimorphs and to gain an understanding of the load bearing capacity as a function of the substrate. The results indicate that thin substrates, on the order of 0.1 mm, with a high modulus, on the order of 200 GPa or more, provide the largest displacements and load bearing capacity. Both classical laminate plate theory and experimental results are used to support this conclusion. The experimental tests used a four point bend setup to load the unimorphs through their entire range of deflection and quantified their load bearing capacity throughout this range. These results were compared to Classical Laminate Plate Theory, in terms of loading and curvature, with good agreement. The primary application of this research is for use on small unmanned vehicles, but these results can be expanded to other Macro-Fiber Composite applications as well. [ABSTRACT FROM AUTHOR]

Hysteresis is an important nonlinear effect exhibited by the Macro Fiber Composite (MFC) that is testified from experimental study. In order to interpret the characteristic accurately, various models were proposed previously, in which the Bouc-Wen model has gained more interest because of its capability to match a wide class of hysteretic systems. However the model consists of a set of differential equations where multi parameters present need to be estimated simultaneously. In view of this, the present study sets out to propose a more efficient Genetic Algorithm (GA) and a simplified Bouc-Wen model on the one hand, and on the other, the GA is applied to the model to enhance the accuracy and efficiency of the parameter estimation. Finally a large number of experimental data are used to testify the proposed approach more efficient and accurate than the other conventional methods. Also suggested are the implications of the present study on other hysteretic models or other complex mathematical models. [ABSTRACT FROM AUTHOR]

The primary objectives of this work are about the experimental study on the nonlinear electromechanical behaviour of the macro fiber composite (MFC), and to analyse the affecting factors of the inconstant parameters d33 and d31 which can arouse nonlinearities of MFC. Both longitudinal and transverse output strains are measured by actuating the MFC specimen under different DC voltages and a range of peak-to-peak sinusoidal voltages (VPP) at various frequencies, which can investigate how the voltage amplitude and frequency affect nonlinear hysteretic behavior. The experimental results of both DC voltages and AC voltages indicate that the relationship of the applied voltage and output strain displays nonlinear hysteretic behavior. The responses of the AC voltages also indicate that hysteresis nonlinearity behaviour of the MFC actuator is sensitive to the varying voltage amplitude and frequency. The higher the voltage and frequency are, the more obvious the hysteresis phenomenon are. [ABSTRACT FROM AUTHOR]

Insufficient service life and the resulting need for battery replacements have been a great challenge for implantable electronic devices. This is particularly true for animal tracking applications, because recapturing animals is often unlikely once they are released to the wild. To tackle this problem, we developed a biomechanical energy harvester that uses a Macro Fiber Composite™ (MFC) piezoelectric beam to harvest the mechanical energy from animals' body bending movements as the power source for implantable and wearable devices. Prototypes of an underwater acoustic transmitter using this technology were subdermally implanted into juvenile white sturgeon and their energy harvesting performance was evaluated through the devices' transmissions. The fish successfully recovered from the implantation surgery and freely swam inside a tank. The transmitter prototypes in the fish continually transmitted signals for a period up to 5 weeks. A benchtop test setup was also created to emulate the fish's body bending, estimate the device's energy harvesting performance in the live fish, and perform accelerated fatigue testing of the energy harvester by applying test parameters learned from a video study of the fish's body movement and behavior characteristics. The gradual depolarization of the piezoelectric ceramic material in the MFC under cyclic mechanical loading was the main limiting factor for the life span of the energy harvester. Pathways for improvement are proposed to achieve long-term efficacy of powering implantable and wearable electronic devices. [Display omitted] • Developed an implantable, lightweight, biomechanical energy harvester that successfully powered an integrated microelectronic device. • The host animal fully recovered from the implantation surgery and freely moved about without any inhibitions for an extended period. • The durability and failure modes of a piezoelectric energy harvester in an aquatic animal host under quasi-realistic conditions were investigated. • The host animal's physiology and behavior were investigated and quantified to guide the design of the prototype. [ABSTRACT FROM AUTHOR]

Impact damage has been identified as a critical form of defect that constantly threatens the reliability of composite structures, such as those used in aircrafts and naval vessels. Low-energy impacts can introduce barely visible damage and cause structural degradation. Therefore, efficient structural health monitoring methods, which can accurately detect, quantify, and localize impact damage in complex composite structures, are required. In this article, a novel damage detection methodology is demonstrated for monitoring and quantifying the impact damage propagation. Statistical feature matrices, composed of features extracted from the time and frequency domains, are developed. Kernel principal component analysis is used to compress and classify the statistical feature matrices. Compared with traditional principal component analysis algorithm, kernel principal component analysis method shows better feature clustering and damage quantification capabilities. A new damage index, formulated using the Mahalanobis distance, is defined to quantify impact damage. The developed methodology has been validated using low-velocity impact experiments with a sandwich composite wing. [ABSTRACT FROM PUBLISHER]